1. Field of the Invention
The present invention relates to a resin circuit board and, more particularly, to a resin circuit board including conductor patterns separated by a thermoplastic resin layer and connected to each other with an interlayer-connecting conductor.
2. Description of the Related Art
In recent years, multilayer circuit boards including three-dimensional wiring conductors have been widely used in various applications. Although ceramic multilayer circuit boards having a layered structure of ceramic layers and conductor patterns have been frequently used, resin circuit boards having a layered structure of resin layers and conductor patterns also have recently been used.
In resin circuit boards including an insulating resin layer, the resin layer is formed of a thermoplastic resin having a melting point of 250° C. or more, such as a liquid crystal polymer (LCP) or polyetheretherketone (PEEK).
In general, conductor patterns are patterned conductor foils, such as Cu foil.
One proposed resin circuit board containing a thermoplastic resin includes, as thermoplastic resin layers, thermoplastic resin films composed of 65% to 35% by weight of polyetheretherketone resin and 35% to 65% by weight of polyetherimide resin and, as conductor layers (conductor patterns), Cu foil (Japanese Unexamined Patent Application Publication No. 2003-332749).
In this resin circuit board, the thermoplastic resin layers and the conductor layers are different in terms of thermal expansion coefficient. A difference in thermal expansion coefficient can cause a problem, such as warping or distortion, in the resin circuit board. Warping or distortion may result in products that do not meet a standard, unstable mounting of electronic components, and other defects.